If students can be swiftly expelled for plagiarism or dealing drugs, the same punishment should be inflicted if there’s enough evidence to suggest they pose a threat to others. Oh but his reputation! That’s really where he suffers. My advice is, if he’s worried about his reputation, don’t rape anyone.
Or accept this new reputation, kid. This is the life you have chosen when you do things contrary to the reputation you wanted for your life. It's just the outward appearance of inside character. It usually isn't wrong.